土壤有機質特異組成及含量對非離子有機化合物吸持行為之研究

The influence of distinctive soil organic matter composition and content on the sorption of nonionic organic compounds

黃慧貞(Hui-Chen Huang)

指導教授 ： 李俊福

國立中央大學/工學院/環境工程研究所/博士(2006年)

摘要

二十世紀柒零年代以來，大量農藥及工業有機廢棄物開始危害環境，許多未經處理即排入環境中之有機污染物造成土壤污染。土壤有機質之來源互異，組成複雜，對於非離子有機污染物在土壤中之傳輸行為具有決定性之影響。
本研究分為三大主題來探討土壤有機質之特殊組成對於非離子有機污染物傳輸行為之影響。第一部份乃探討土壤有機質中之高表面積碳黑物質(HSACM)對於低濃度之非離子有機污染物非線性吸附行為。本研究以物理方式替代常用之氧化或熱處理方式來分離有機質中碳黑物質，並以土壤及HSACM進行非離子有機污染物之吸附行為研究，結果中發現HSACM為一高表面積碳黑成份，是有機質中對非線性吸附造成貢獻之主要因子，系統中存在雙重吸附質時，會抑制HSACM之吸附，表示HSACM對非離子有機污染物之作用機制為一吸附作用；此部份並以高分子模擬有機質之官能基，進行氣態吸附實驗，實驗結果發現在低濃度下，有機物之極性及有機質中之官能基會影響吸附行為。
第二部份探討有機質芳香性組成對於不同結構之非離子有機化
合物吸附行為所造成之影響。以已知組成之染料或界面活性劑來模擬真實之土壤有機質結構，以簡化有機質複雜組成之變因。實驗選用兩組不同結構但具有近似水溶解度之化合物來進行，研究結果顯示，有機質組成和有機污染物之結構相近者，有機污染物將有較高的分佈係數。溶解度參數被用來解釋不同有機污染物在不同組成之土壤有機質中之的分佈行為，溶解度參數相近之有機化合物間會有較大之分佈係數。
第三部分的研究主題為探討低含量土壤有機質所形成之吸附性表面其吸附非離子有機化合物時所顯現之特異分佈係數值，實驗選有四種苯環化合物及有機氯農藥進行，研究結果指出，有機質在單層吸附時，形成吸附表面的行為和一般分佈作用不同，土壤無機相在有機質單層包覆時會影響有機化合物之分佈作用，使非離子有機污染物有較大之分佈係數。

關鍵字

吸附表面 ； 芳香性 ； 特定作用力 ； 碳黑物質 ； 土壤有機質

並列摘要

Since 1970, unlimited usage of pesticides and organic compounds leads to soil contamination. The compositions of soil organic matter originated from various areas were disparity and affect the transportation of nonionic organic compounds (NOCs) in soil critically.
This study explores the influences of specific composition and content in soil organic matter (SOM) on the fates of organic compounds in soil. The first part investigated the contribution of high-surface-area carboneous material (HSACM) to nonlinear sorption at low relative concentration of nonionic organic compounds. The physical non-destructive method was substituted for oxidation or thermal treatment to isolate the HSACM. The sorption of NOCs to soils and HSACM was investigated. The BET data shows the high surface area of HSACM. The existent of HSACM contributed significantly to nonlinear sorption of SOM at low relative concentration of nonionic organic compounds. In binary-solute system, the uptake of a solute by soils at low NOCs concentration may be suppressed by other solutes (i.e., cosolutes). The competitive sorption demonstrated that the mechanism responsible for the uptake of NOCs by HSACM is attributed to adsorption but partitioning. In order to evaluate the effect of specific functional groups in SOM on the adsorption of organic compounds, especially at low pressure, we chose polymers with known functional groups as the adsorbents in this experiment to simplify the complex characteristics of soil organic phase. In all experimental data, the adsorption isotherms show nonlinearity with concave-downward curvatures at low relative pressure but exhibit a linear shape at higher pressure. The nonlinearity of isotherms coincides with solute polarity. The sorption capacities are greater for polar solutes than for nonpolar solutes. The nonlinear capacity increases progressively with increasing solute polarity for other solutes.
The second part elucidated the influences of solid-phase organic constituents on the partition of aliphatic and aromatic organic contaminants. The influence of natural organic matter (NOM) constituents on contaminant distribution coefficients was evaluated by determining the Koc values of aromatic and aliphatic organic compounds (solutes) with clays modified with both aromatic- and aliphatic-rich organic constituents. The studied compounds consisted of naphthalene, phenanthrene, n-pentane, and 2,3,4-trimethylmethane; the solid samples comprised two clays with little organic content, kaolinite and Ca-montmorillonite. For solutes of comparable water solubilities, the organic-carbon normalized distribution coefficients (Koc) of the aliphatic solutes between sorbed aliphatic organic matter and aqueous solution slightly exceed those of the aromatic solutes. By contrast, the aromatic solutes exhibited higher Koc values than did the aliphatic compounds with sorbed aromatic-rich organic matter. The difference in Koc values could be attributed to either comparable solubility parameters or the difference in the chemical structure between nonionic organic solutes and specific components of the simulated NOM.
The objective of last part was to investigate the NOCs uptake to soils with low content SOM. The extraordinary high Koc values of NOCs uptake to soils with low SOM content were research. The influence of SOM contents on contaminant distribution coefficients was evaluated by determining the Koc values of BTEX and organic-chloride pesticides (solutes) with clays modified with aromatic dyes. The experimental data shows the uptake of NOCs to soil with extremely low organic matter content is quiet different from partitioning. The uptake of NOCs to mineral coating with a thin-slice SOM will be affected by mineral. The adsorption mechanism will increase the Koc values of NOCs.

並列關鍵字

specific interaction ； soil organic matter ； High-surface-area carboneous material ； sorptive surface ； aromatic

參考文獻

[2] Zhou, H., Li, H., Xu, O. “Partition of Nonpolar Organic Pollutants from Water to Soil and Sediment Organic Matters”, Environ. Sci. Technol., 29, 1401-1406 (1995)

[3] Farar, D.M., Coleman. J. D. “The correlation of surface area with other properties of nineteen British clay soil”, Soil Sci., 18, 118-124 (1967)

[4] Chiou, C. T., Lee, J.-F., Boyd, S. A. “The Surface Area of Soil Organic Matter”, Environ. Sci. Technol., 24, 1164-1166 (1990)

[6] Stark, F. L. “Investigations of chloropicrin as a soil fumigant” New York (Cornell) Agric. Ezp. Stn. Mem. 178, 1-61 (1948)

[7] Hanson, W. J., Nex, R. W. “Diffusion of ethylene dibromide in soils” Soil Sci. 76, 209-214 (1953)